This invention relates in general to automotive vehicles having tandem axles and more particularly to a bearing arrangement for the input shaft of an axle center for a forward axle in such a vehicle.
Many large over-the-road trucks have tandem drive axles, with each axle being equipped with an axle center containing a differential and axle shafts that transfer power from the differential to road wheels at the ends of the axle. The forward axle center, in contrast to the rear axle center, contains aligned input and output shafts that are connected through an interaxle differential and a through shaft that is aligned with and coupled directly to the output shaft. These shafts transfer power from the drive shaft of the vehicle to the rear axle center. The input shaft also carries a helical gear that drives a pinion shaft forming part of the differential for the forward axle center. The input shaft should rotate with stability, that is to say, its axis of rotation should remain fixed with respect to the housing in which it rotates. But achieving stability demands a good measure of skill and time during the assembly of the axle center, primarily to adjust the bearings that support the input shaft. Typically, this involves selecting shims of the correct size and installing them behind the cup (outer race) or behind a cup carrier or cup follower for the forwardmost of the two bearings that support the input shaft.
In those axle centers which have the cup of the front bearing actually within the housing itself—as opposed to within a cup carrier—a loose fit often exists between the cup and the housing to facilitate adjustment of the bearings that support the input shaft. This allows the cup to turn within the housing, causing wear which produces an even looser fit and less stability for the input shaft.